Wastewater treatment is a matter of continuing concern, particularly as the population increases and the availability of potable water decreases, Reuse of wastewater from both industrial and municipal sources as well as agricultural effluents is a necessity.
New governmental regulations and statutes are requiring immediate improvements in the treatment of effluent from all types of wastewater treatment facilities.
In the handling and treatment of sewage, a collection network of sewer lines pick up the raw sewage and deliver it to a treatment plant.
The ultimate goal in the treatment of the raw sewage is to separate all impurities, both organic and inorganic, from the water and return the treated, uncontaminated water in pure form into the ground water or into a river or stream. This ultimate goal is seldom or never achieved, however, it remains a goal that is not only desirable but one that government regulations insist on.
Raw sewage in the collection system begins to breakdown on its travel to the sewage treatment plant due to the action of the anaerobic bacteria on the organic solids. The length of travel to the treatment plant influences the degree of decomposition. Often times the sewage arrives at the plant in a very septic condition causing problems in treatment and obnoxious odors.
Odors in sewage are usually a result of putrefaction of solids in the wastewater. The putrefaction process can produce a variety of odorous compounds. The most prevalent and most obnoxious are those resulting from hydrogen sulfide that is produced by the breakdown of sulphur compounds. Hydrogen sulfide not only produces obnoxious odors, but also can cause devastating corrosion of concrete structures. The hydrogen sulfide generated in the sewer system reacts with oxygen in the presence of oxidizing bacteria and in the humid atmosphere above the water surface in a wet well or other enclosed structure, to produce sulfuric acid as a condensate on the walls of the sewer lines, wet well, or other structure. This acid is strong enough to destroy even the best concrete. If this hydrogen sulfide can be eliminated from the system, both obnoxious odors and corrosion can be controlled.
In the handling of sewage in the collection system, it is possible to commence the treatment of the raw sewage in the collection system and prepare it for final treatment. This pretreatment can reduce the load on the treatment plant and expedite the treatment time.
All of the biological treatment processes are most efficient when the influent wastewater is fresh coming into the treatment plant. Treating efficiency may be adversely affected and the biological process upset if the wastewater becomes septic